Rabbits predominantly rearrange the most 3'VH gene (VH1); thus combinatorial diversity is very limited. In man and mouse, the most 3'DH gene, DQ52, is preferentially rearranged early in B-cell development. To test whether this preference for rearranging a DH gene segment based on 3' end proximity exists in rabbit, we cloned and sequenced the rabbit DQ52 gene. The 11 base pair coding region sequence is identical to a published mouse DQ52, and 81.8% similar to the human sequence. It is localized approximately 805 bp upstream of the JH1 gene. However, the 3' recombination signal sequence has an atypical nonamer. We prepared mRNA from 15- to 28-day fetal rabbits and amplified expressed VDJ sequences of mu mRNA by RT-PCR. The PCR products with VDJ rearrangements were cloned and sequenced. As expected, 44 of 45 VDJ sequences reflected use of the 3' VH1a2 gene, but the DQ52 gene was utilized very infrequently, if at all. We found only one VDJ sequence from 28-day fetal liver B-cells with 8 bp that matched the germline DQ52 sequence. Instead of expressing DQ52, another DH gene, Df was frequently expressed. We cloned the genomic Df gene and localized it about 32 kb upstream of the JH region. Thus, in contrast to man and mouse, rabbits preferentially express a DH gene located in the middle of the DH region early in B cell ontogeny. This may correlate with more frequent initial rearrangement of VH to DH in rabbit B cells.

译文

兔子主要重新排列最3'VH基因(VH1);因此组合多样性非常有限。在人和小鼠中,最3'DH基因DQ52在B细胞发育早期被优先重排。为了测试在兔子中是否存在基于3'末端邻近性重新排列DH基因片段的偏好,我们克隆并测序了兔子DQ52基因。 11个碱基对的编码区序列与已发布的小鼠DQ52相同,而与人类序列相似的为81.8%。它位于JH1基因上游约805 bp。然而,3'重组信号序列具有非典型的九聚体。我们制备了15至28天胎兔的mRNA,并通过RT-PCR扩增了mu mRNA的表达VDJ序列。具有VDJ重排的PCR产物被克隆并测序。不出所料,在45个VDJ序列中有44个反映了3'VH1a2基因的使用,但DQ52基因很少被使用,如果有的话。我们从28天胎儿肝B细胞中发现只有一个VDJ序列,其8 bp与种系DQ52序列匹配。 Df经常表达而不是表达另一个DH基因DQ52。我们克隆了基因组Df基因,并将其定位在JH区上游约32 kb处。因此,与人和小鼠相反,兔子在B细胞个体发育中优先表达位于DH区中部的DH基因。这可能与兔B细胞中VH到DH更频繁的初始重排有关。

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